1. Field of the Invention
The present invention relates to a liquid discharge head, which to discharge a desired liquid generates bubbles by applying thermal energy to the liquid, and a liquid discharge apparatus that uses the liquid discharge head, and to a method for correcting the volume of liquid discharged by the liquid discharge head.
The present invention can be applied for an apparatus such as a printer, a copier, a facsimile machine that includes a communication system, or a word processor for which is provided a printing unit, which records data on a recording medium composed, for example, of paper, thread, fiber, cloth, metal, plastic, glass, wood or a ceramic material, or for an industrial recording unit that when assembled includes one or more of the above variety of apparatuses.
xe2x80x9cRecordingxe2x80x9d according to this invention applies not only to the provision for a recording medium of meaningful images, such as characters or graphics, but also to the provision of meaningless images, such as random patterns.
2. Related Background Art
A conventional, well known ink-jet recording method is the so-called bubble-jet recording process, according to which a state change occurs when thermal energy applied to a water-based liquid produces a drastic change in liquid volume (bubbles are generated), and liquid droplets are ejected through discharge orifices and adhere to and form an image on a recording medium. As is disclosed in U.S. Pat. No. 4,723,129, for a recording apparatus employing the bubble-jet recording process, a liquid discharge head that is generally provided comprises: discharge orifices for discharging a liquid; liquid flow paths that communicate with the discharge orifices; and electro-thermal conversion elements provided along the liquid flow paths that serve as energy generation means for discharging the liquid.
According to this recording method, a high quality image can be recorded rapidly with reduced noise, and in the liquid discharge head, the discharge orifices can be assembled to form a high density arrangement. As a result, many outstanding advantages are provided, to include the capabilities of recording high resolution images using a compact apparatus and of performing the easy recording of color images. Therefore, the bubble-jet recording process is employed for many office machines, such as printers, copiers and facsimile machines, and in addition, is employed in industry, such as when it is used in a printing apparatus for textiles.
For the above described liquid discharge head, however, the volume of the liquid ejected from the discharge orifices differs due to production errors during their preparation, and these variances in the volume of the discharged liquid must thereafter be corrected during the remainder of the head manufacturing process. That is, to eliminate the variances, liquid from all the orifices is ejected onto a recording medium, and the dot diameters of the ejected liquid are examined to calculate the volume of the liquid discharged by each discharge orifice. Then, correction data to regulate the fluid discharged are written to a ROM.
When the variances in the volume of the liquid discharged from the discharge orifices are corrected as described above, by actually ejecting liquid during the manufacturing process, immediately after the corrections are made the liquid volume variances are eliminated. However, after some time has elapsed following the corrections, and water in the liquid has evaporated, the effectiveness of the corrections is reduced due to an increase in the viscosity of the liquid. Therefore, over an extended period of time, it is difficult to use small droplets to form high quality images, a procedure that is currently in demand. In addition, while a process can be performed that, to a degree, restores the effectiveness of the variance corrections, this recovery process must be performed frequently. And as a result, not only is throughput reduced, but also, since ink tank capacity must be increased, a compact apparatus can not be obtained.
It is, therefore, one objective of the present invention to provide a liquid discharge head that can form high-quality images for an extended period of time and a liquid discharge apparatus that can use the liquid discharge head, and a discharge volume correction method for the liquid discharge head.
To achieve the above objective, according to the present invention, a liquid discharge head comprises:
an element substrate, on the surface of which a plurality of energy generation elements are arranged in parallel to generate electrical energy that is applied to eject a liquid;
a top plate, which is positioned facing the element substrate and which defines a plurality of liquid flow paths that correspond to the energy generation elements and that communicate with discharge orifices whereat a liquid is ejected;
one or more flow rate detection elements, which are provided for each of the liquid flow paths to detect the flow rate at which the liquid flows along each of the liquid flow paths; and
an energy generation element controller, for controlling, based on the results output by the flow rate detection elements, the condition under which the energy generation elements are driven.
The flow rate detection elements are provided on the liquid flow paths upstream of the energy generation elements.
The flow rate detection elements each include a heat generator and a temperature detector for flow rate detection.
The flow rate detection elements are thermistors.
The flow rate is detected by heating the heat generator before the application of the electrical energy, and by detecting a temperature using the temperature detector after the application of the electrical energy.
The electrical energy is applied as a plurality of pulses.
The condition for the driving of the energy generation elements may be controlled for each of the liquid flow paths, or may be controlled by changing the pulse width of a drive pulse to be applied to each of the energy generation elements.
Further, the condition for driving the energy generation elements may be controlled by driving sub-heaters that are provided for the liquid discharge head and heating the liquid in the liquid flow paths.
The energy generation elements are electro-thermal conversion elements that generate thermal energy for generating bubbles.
Movable members are located along the liquid flow paths, facing the energy generation elements, so that the downstream ends thereof, which are directed toward the discharge orifices, move freely, and the flow rate detection elements are provided for the movable members.
The flow rate detection elements may be provided for walls of a top plate facing the liquid flowing in the liquid flow paths, or may be provided for walls of the element substrate facing the liquid flowing in the liquid flow paths. Further, the flow rate detection elements may be provided in three-dimensional structures that project outward into the liquid flow paths from walls that define the liquid flow paths.
In addition, according to the present invention, a liquid discharge apparatus comprises:
transportation means for transporting a recording medium; and
supporting means for supporting a liquid discharge head, in accordance with the invention, for ejecting a liquid to record an image on the recording medium, and for reciprocally moving perpendicular to the direction in which the recording medium is transported.
According to the present invention, a liquid discharge apparatus may include recovery means for, in accordance with a signal output by each of the flow rate detection elements, performing a recovery process to attract the liquid in the liquid discharge head of the invention.
The words xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are used in this invention to represent the direction in which the liquid flows from a liquid supply source via an bubble generation area (or a movable member) to a discharge orifice, or the direction designated in the above described arrangement.